The overall aims and objectives of the proposed research are several: 1) to understand more precisely the molecular aspects of the interaction of the phosphate ring of cyclic 3 feet,5 feet-nucleoside monophosphates with intracellular enzymes with the ultimate target the normalization of processes which control neoplastic transformation; 2) to devise new potential antitumor and antiviral prodrugs based on cyclic 3 feet,5 feet nucleoside monophosphate; neutral cyclic nucleotide derivatives, and certain 3 feet and 5 feet nucleoside monophosphate diesters; 3) to prepare steriospecifically 0-isotope labeled phosphates of biological interest and then correlate 17-O NMR spectral parameters with phosphorus configuration and conformation; 4) to gain a thorough understanding of the conformational features of the 1,3,2-oxazaphosphoriane ring of cyclophosphamide and diastereomeric ring-substituted derivatives and their realationship to ease of microsomal oxidation potentiation and overall therapeutic selectivity; 5) to survey the synthetic and mechanistic aspects of a newly discovered reaction generating N-substituted azetidines with the potential for preparation of biologically interesting Beta-lactams; 6) to utilize newly discovered and postulated new free radical chain reactions of hydridophosphoranes to prepare pentacovalent phosphorous products not otherwise easily available. To these ends new synthetic methods based on cyclic tervalent phosphorus intermediates will be devised for the preparation of neutral derivatives of 3feet,5 feet-cyclic nucleoside monophosphates with a variety of functionality at phosphorus. Collaborative testing in enzyme, cellular and in vivo systems will be carried out, including the assessment of antitumor and antiviral properties. 1H, 13C, and 31p NMR techniques will be to characterize the phosphate ring conformations of the neutral cyclic nucleotide derivatives, assign phosphorus configuration, and relate geometry to biological activity. NMR techniques similarly will be applied to the 1,3,2-oxazaphosphorinane ring system of cyclophosphamide and key ring-substituted derivatives. 17O NMR techniques will be applied in both systems to molecules prepared by stereospecific reaction pathways.